Hammer-mill bed plate and teeth therefor



May 6, 1952 w. M. PERRY HAMMER-MILL BED PLATE AND TEETH THEREFOR Filed June 30, 1947 ATTOENEY I Patented May 6, 1952 OFFICE HAMMER-MILL BED PLATE AND TEETH THEREFOR Willis M. Perry, Adelaide, Wash.

Application June 30, 1947, Serial No. 757,969

1 Claim. 1

This invention relates to hammer mills adapted for use in making wood fiour, and has special reference to the form and construction of the teeth of such a mill.

The objects of my invention are, first, to increase the efficiency of such a mill; second, to form the teeth thereof in such manner that the wood fiour does not accumulate in the teeth nor may the saw dust pass thereover without being pulverized; third, to form the cutting teeth of short lengths whereby, if one is broken it may be quickly removed and another tooth inserted in its place; and fourth, to form the teeth with a half dovetail to facilitate the machine work on the bed plate and on the teeth themselves, and to economize on the material used in making the teeth.

I attain these and other objects as will readily be seen by those familiar with the art, by the devices and arrangements illustrated in the accompanying drawings, in which:

Fig. 1 is a cross-section of my improved wood fiour hammer mill; Figs. 2 and 3 are inside elevations of the side plates, illustrating the grooves therein for holding the bed plates and the outlet screen; Fig. 4 is a perspective view of portions of the bed plate, showing teeth mounted therein; Fig. 5 is a section of a portion of the wheel disks and hammers; and Fig. 6 is an enlarged view of a portion of the bed plate with teeth therein and the hammer sweeping therepast.

Similar numerals of reference refer to the same parts throughout the several views.

The common practice of making wood flour is to make the cutting face of the teeth radial, but I have found that, by inclining the said face some five to fifteen degrees from said radial line, the rate of output of the mill, in flour of the desired fineness, is increased about 30%. This facial angle may be reduced very slightly below the said five degrees without too serious results, but if it is increased beyond fifteen degrees I find that the output is reduced and the sawdust accumulates in the base of the teeth. If the facial angle is'reduced so as to reach or even extend beyond the radial line, the output of flour is materially reduced as the teeth no longer cut the saw dust into the fibrous condition desired in wood fiour but rather tend to crush it.

Referring, now, to the drawings, the mill comprises a metal casing with sides III and a top plate I I. A cover I2 is hinged at I3 to the said top plate II, said cover comprising a segment of a circle and having side plates I I. The rapidly rotating shaft I5 is suitably journaled in the side plates I0,

or otherwise, and carries a series of circular disks I6, separated from each other. The disks I6 are provided with symmetrically placed bolts II near their peripheries, each said bolt passing through all said disks or plate I6. Each bolt N forms a pivot on which the hammers are loosely hung, and each hammer is composed of two separate plates I8 and I9, lying side by side in contact with each other.

The inner sides of the side plates I0 (Fig. 3) are each provided with an arcuate groove 20, centered on the axis of the shaft I5, and the side plates I4 of the cover (Fig. 2) are each provided with a similar groove 2I, having the same radius and center as the said groove 20 when the cover I2 is in closed or operating position, as shown.

A screen 22 extends across the machine and is mounted on side plates 23 which are curved to the-same axial center as the groove 20, and which may be slid into place into said grooves 26 when the said cover I2 is opened.

A tooth bed plate 24, also curved on said axial center and radius, extends across the machine and is provided with side flanges 25 (Fig. 4.) adapted to fit in the said grooves 20, being inserted therein when the cover I2 is opened.

An exactly similar bed plate 26 is inserted in the grooves 2| of the sides I4 of the cover I2, and is inserted therein when the cover is open.

Referring now to Figs. 4 and 6, it will be seen that the inner curved surface of the bed plate is provided with a series of teeth 21. These teeth 21 are of mild steel and are all of the same shape in relation to the respective radii from the center of the shaft I5. Each tooth is formed with a top surface 28, inclined downward in the direction of travel of the hammers I8; a back face 29; a base 30 at right angles to the face 29; and a front face 3| which makes an acute angle with both the base 30 and the back face 29. In

practice the face 28 may make an obtuse angle of about with the radius; the side 29 makes about 24 with the said radial line, and the side 3| makes an angle therewith of from 5 to 15 on the side thereof towards the approaching hammers.

The three faces 29, 30 and 3| are accurately finished and are uniform in all the teeth, and form the sockets or grooves adapted to firmly hold the cutting teeth 32. The two faces 29 and 3 I, together with the base 30, form a half dovetail in which the said cutting teeth 32 are firmly held.

The cutting teeth 32 fit accurately in the said dovetail space, being inserted therein from the side edges of the bed plates 24 and 26, when the cover I2 is opened and the said plates removed from the machine. These cutting teeth 32 are made of the best steel and may be of short lengths, so that if a tooth is broken, it may be replaced by a short length of new teeth. The form of these teeth 32 follows the same lines as the teeth 21 above described, and thus present a sharp cutting edge 33 of about 60 to the saw dust in the machine.

It is my intent that this patent shall cover not only the specific construction thereof described in the embodiment of my invention which I have chosen for its disclosure in the above specification, but such colorable changes and modifications thereof which do not depart from the spirit of my invention as outlined in the appended claim.

The size and spacing of the teeth in the machine may be varied to attain the best results with different species of wood, and with variations in the quality of the saw dust, and with the type of Wood flour desired.

Having described my invention, what I claim and desire to secure by Letters Patent is:

In a wood-flour hammer mill, the combination with a frame having side Plates, a rotor journalled therein, and a series of hammers freely swinging thereon, in combination with a curved bed plate removably held in circumferential grooves in said side plates, and concentric with said rotor, and extending across said mill; a series of dove-tail grooves in and across the concave side of said bed plate, the front side of said 4 sides, the inner face of said curved plate adjacent said grooves making an angle of approximately with the same radius and in the same direction; and a series of teeth mounted in said grooves and extending therefrom, each tooth fit ting said grooves and based on the base thereof, and having a front face fitting the front face of said groove and extending inwardly coplanarly therefrom, a rear face at right angles to said base and fitting the rear face of said grooves, and an inner coplanar surface extending from said rear face to said front face and being an extension of said inner face of said bed plate, thereby forming REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 214,254 Lippy et al. Apr. 15, 1879 283,529 Stewart Aug. 21, 1833 748,536 Schoellhorn et a1. Dec; 29, 1903 1,074,040 Bettington 1 Sept. 23, 1913 1,141,825 Pethoud. June 1, 1915 1,307,761 Shelton June 24, 1919 1,354,855 Simpson Oct. 5, 1920 1,375,862 Shelton Apr. 26, 1921 1,420,354 Williams June 20, 1922 1,568,520 Martens Jan. 5, 1926 2,130,312 Pickel Sept. 13, 1938 FOREIGN PATENTS Number Country Date 355,748 Great Britain Aug. 28, 1931 569,777 Great Britain June 7, 1945 

